What Pink Minccino said is correct. I would also like to point out the following.
Poffins may come out better when made with a friend. If you can connect with other people, do. Note, however, that certain Berrys do not mix well with each other, or cancel each other out.
Dry weakens Spicy, Spicy weakens Sour, which weakens Bitter, which weakens Sweet, and Sweet weakens Dry to complete the circle.
Sources are the Pokemon Platinum Offical Game Guide, and experience.